1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive decreasing head temperature to increase fly-height during seek operation.
2. Description of the Prior Art
In disk drives, a head is actuated radially over a disk in order to access a target track recorded on the disk. The head is attached to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor during seek operations. As the disk rotates, an air bearing forms which causes the head to “fly” just above the disk surface while writing magnetic transitions during a write operation, or reading the magnetic transitions during a read operation. The head comprises a slider having an air bearing surface and an integrated transducer, such as a write coil and a magnetoresistive read element.
Decreasing the distance between the transducer and disk surface (fly-height) improves the signal-to-noise ratio in the read signal, thereby enabling higher recording densities (radial tracks per inch and linear bits per inch). To this end, designers have exploited the expansion properties of the head (e.g., the slider and/or transducer) by incorporating a heater to control the temperature of the head and thereby the fly-height. Increasing the temperature causes the head to expand, thereby moving the transducer closer to the disk surface. However, decreasing the fly-height increases the chances the head will collide with the disk causing damage to the head and or recording surface. This is of particular concern during seek operations due to the increased velocity of the head with respect to the disk and the potentially large fluctuations in fly-height due to vibrations in the actuator arm.
U.S. Pat. No. 5,991,113 discloses a disk drive which reduces the head temperature during a non-operating or “sleep” mode (not performing write or read operations), thereby increasing the fly-height to help prevent head/disk contract. However, the relatively slow transient response of the heater can adversely impact access time of the disk drive, particularly with respect to seek operations. For example, the cooling period of the heater can delay the seek operation, and the preheating period can delay the write/read operation after the seek.
There is, therefore, a need to reduce the head temperature to increase fly-height during seek operations without significantly increasing the access time of a disk drive.